Hillary Clinton is starting to lose her overwhelming lead with super-delegates, the Democratic party officials whose votes she is counting on to help her close the gap with Barack Obama.

Obama has received a steady flow of new backers in recent days while building a streak of 11 straight primary victories. After once leading Obama by a 2-to-1 ratio in the super-delegate chase, Clinton now has 241 to his 181, according to the latest Associated Press tally.

Most unnerving for Clinton is the trickle of super-delegates who have defected from her corner to Obama's. The shift comes as Clinton failed to deliver a telling blow on Obama in their penultimate televised debate before the Texas and Ohio primaries on March 4.

Latest polling shows the candidates separated by two percentage points in Texas, well within the margin of error, and seven points in Ohio.

The Clinton campaign had hoped the debate would offer her an opportunity to halt Obama's momentum. Instead she came under fire for allegedly plagiarising part of a speech made by former candidate John Edwards.

When asked about the potential influence of the super-delegates during Thursday night's debate at the University of Texas in Austin, both candidates appeared to pull back from the brinksmanship that has been developing over the issue.

"I think that it will sort itself out," Clinton said. "We will have a nominee, and we will have a unified Democratic party, and we will go on to victory in November."

Obama said that for the nomination to be decided by backroom deals would sully the process. "The American people are tired of politics that is dominated by the powerful, by the connected. They want their government back," he said.

In New Jersey, where Clinton won by 13% this month, two Democratic super-delegates have shifted to Obama and nine Democratic leaders endorsed him. "Barack can help unite this country and help us embrace our diverse nation," said super-delegate Christine Samuels.

Super-delegates who represent areas won by Obama are facing pressure to declare for him. One Clinton super-delegate, Texas congresswoman Sheila Jackson Lee, said colleagues had urged her to support Obama if he wins her district in the primary.

But she said: "I want voters to be at ease that their votes truly count. But I also want them to respect each of us [super-delegates] individually for how we have perceived America's future to be."

Outside New Jersey Obama picked up five new super-delegates after his victories in Hawaii and Wisconsin. More than half of the 795 super-delegates had declared for a candidate as of last week.

The most dramatic moment in the debate came when Clinton tried to exploit the charge that Obama had plagiarised someone else's words in speeches.

"Lifting entire passages from someone else's speeches is not change you can believe in," she said, "it is change you can Xerox."

The line was met with boos from the audience.

Asked what had been the most testing moment in her life, she said everyone knew she had lived through "challenges and crises" but added: "Whatever happens we're going to be fine. You know, we have strong support from our families and our friends. I just hope that we'll be able to say the same thing about the American people, and that's what this election should be about."

The line is similar to one used by Edwards in December. He said: "All of us are going to be just fine no matter what happens in this election. But what's at stake is whether America is going to be fine."